Re-enable resource graph definer propagation (targeted)

[avrabe]

Part of #69, depends on #73

Task

The resource graph needs to propagate definers through re-export chains so that callee_defines_resource is correctly set to false for runner→intermediate adapter sites.

A previous attempt caused an xcrate regression. The fix: only propagate when from_comp is a confirmed re-export target (another component imports from it) AND the export interface differs from the import interface.

Implementation

Files: meld-core/src/resource_graph.rs

After the existing removal pass in ResourceGraph::build, add targeted propagation:

let mut changed = true;
while changed {
    changed = false;
    for ((from_comp, import_name), (to_comp, _)) in resolved_imports {
        // Only propagate for confirmed re-export targets
        let is_reexport_target = resolved_imports.values()
            .any(|(target, _)| *target == *from_comp);
        if !is_reexport_target { continue; }
        
        // Find defined resources for to_comp matching import_name
        // Propagate to from_comp's [export] interfaces that carry same resource
        // Guard: export interface must DIFFER from import interface
    }
}

Branch

feat/per-component-handle-tables

Acceptance

cargo test --package meld-core passes including the xcrate fixture.